Zero-turn radius vehicle with steerable front wheels

ABSTRACT

The present invention relates to a zero turning radius vehicle having at least one steerable front wheel and a multistage steering input system separately capable of steering the at least one front wheel and selectively driving the drive wheels. A front wheel steering system comprises at least one oblongated sprocket meshingly connected to a steering shaft. An engagement cam system provides the ability to selectively, independently couple the steering wheel to pump arms driving a first and second drive wheel. A steering cam shaft comprises at least one steering cam that acts on at least one bearing. Once the engagement cam system rotates the at least one bearing into place to receive the at least one steering cam, rotation of the steering cam independently alters the speed of one drive wheel in relation to the other drive wheel in response to steering input provided by the operator.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application claims priority from U.S. ProvisionalApplication Ser. No. 60/511,529, filed on Oct. 15, 2003 titled“Zero-turn radius lawnmower with steerable front wheels.”

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a zero turning radiusvehicle. Specifically, the present invention provides a zero turningradius vehicle with outboard steerable front wheels andindependently-driven rear wheels.

2. Background

Whether a lawn mower is utilized commercially or for personal use,efficient operation is essential. In commercial settings, time is moneyand contractors desire to finish a yard as quickly as possible so theymay complete more jobs in a day. Similarly, a homeowner wants to finishhis yard as soon as possible so that he may move on to more enjoyableactivities. Zero-tuning-radius (“ZTR”) vehicles adapted to include amower deck have become particularly popular in the lawn care industrybecause their tight cornering capability obviates the constant need toshift gears from forward to reverse or to drive in a wide loop in orderto turn around, as is necessitated by the large turning radius of anon-ZTR vehicle.

Zero turning radius vehicles known in the art have the capability tomake turns having a center of rotation at the midpoint between theindependent drive wheels. This is accomplished by driving theindependent drive wheels at different speeds, and even in differentdirections, with respect to each other. ZTR vehicles are particularlyuseful in the lawn care industry. ZTR vehicles require the operator tofacilitate steering of the vehicle by maneuvering separate leversresponsible for controlling the independent drives of each wheel ratherthan providing a steering wheel. However, many users find the dual leversystem extremely difficult to operate given that the vast majority ofvehicles with which the average person is familiar utilizes a steeringwheel as the steering input. The dual-lever systems typically involve avery lengthy “learning curve” to enable the user to become accustomed toits operation.

In commonly known ZTR vehicles, the drive wheels, or locomotion wheelsare the rear wheels. These rear ground-engaging, independent drivewheels also provide the means of steering the vehicle. As a result, itis not necessary for the front wheels to be steerable. Therefore, casterwheels are typically used for the front ground-engaging wheels. Casterwheels spin 360 degrees about a vertical axis of rotation, but are notsteered. Rather, they simply respond to the movement and direction ofthe vehicle as dictated by the drive wheels.

The problem with these non-steerable front wheels, however, is that“crabbing” is a major problem. For example, when a ZTR vehicle usingnon-steerable caster wheels as front ground-engaging wheels is drivenlaterally across the side of a hill, the gravitational force of the lawnmower tends to pull the vehicle down the side of the hill. The naturaltendency of the caster wheels is to turn down the hill even if theoperator does not wish to turn in that direction. To counteract thisphenomenon, users of common ZTR vehicles must continually provideintermittent steering inputs with the levers to maintain the ZTR vehicleon the hill. The result is a series of zigzag motions (or “crabbing”) asthe vehicle traverses the hill or an angling of the vehicle as it movesacross the hillside.

In systems that purport to “steer” the front wheels, the front wheelsare simply linked at all times to the drive wheels so that some amountof “bias” is always present. “Bias” in this context refers to asituation where the rear drive wheels are being operated at differingspeeds and/or direction from each other. Moreover, the steering wheel insuch systems is used at all times as an accelerator. Every steeringinput provides bias to the drive wheels. There is no mechanism allowingthe steering wheel to not be used as a biasing accelerator. This wouldappear to cause major problems for the user. First, it could bedifficult to control the vehicle since any steering input isautomatically translated into a bias condition. Second, constantlybiasing the drive wheels could create the need for constant steeringinputs, always correcting and counter-correcting for each previoussteering input. Linear lines of travel could be difficult, if notimpossible, to achieve. Moreover, constantly biasing the rear wheelscould tear up the turf.

The need exists for a ZTR vehicle that can actually steer the frontwheels of the vehicle separate from the drive wheels in order to providemore efficient and effective operation and reduce or eliminate thecrabbing phenomenon. The need also exists for a ZTR vehicle that is moreuser-friendly so that a consumer need not spend an inordinate amount oftime learning how to operate the vehicle. Also, the need exists for aZTR vehicle that provides a multistage steering input to steerable frontwheels and to drive wheels in a predetermined relationship to eliminatethe constant bias in the drive wheels, thus providing a much morenatural vehicle similar to other steered-wheel vehicles in use.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to a ZTR vehicle providing steerablefront ground-engaging wheels. The vehicle comprises a frame thatincludes a first and second steerable rotatably-mounted frontground-engaging wheel and two rotatably-mounted ground-engaging drivewheels. It is noted that at least one steerable front wheel is all thatis required. However, two steerable front wheels are typical of thesevehicles and so the discussion will describe an apparatus having twosteerable front wheels. This shall not, however, be deemed to limit theinvention to requiring two steerable front wheels. The first and secondsteerable front wheels are connected to the fame via wheel yokes andcaster pivot mounts. The frame further includes an engine that providespower to operate the vehicle and two hydraulic pumps, each pumpindependently connected to one drive wheel.

A steering system is provided through which a multistage steering inputcan be provided to the vehicle. In the preferred embodiment, thesteering system comprises a steering device that is a steering wheelrotatable in clockwise and counterclockwise directions. Obviously,however, any form of steering device (dual levers, single levers,joysticks, and so forth) is possible. The steering device provides amultistage steering input to multiple systems of the vehicle. In thepreferred embodiment, the steering input provides input in two stages-afirst input to a front wheel steering system and a second input to adrive wheel locomotion system in a manner that selectively alters thespeed of one drive wheel in relation to the other. The steering systemdoes not always engage the drive wheel locomotion system. Rather, it canselectively engage it through the use of an engagement cam system.

In the front wheel steering system, the steering device is connected byone or more steering shafts to at least one wheel sprocket. Again, forthe sake of convenience, a vehicle having two front wheels is described,and so the discussion involves a first and second wheel sprocket. Thisshall not be deemed to limit the invention to requiring two wheelsprockets. The first and second wheel sprockets are connected to thecaster pivot mounts of the first and second steerable front wheels,respectively. Preferably the wheel sprockets are ellipsoidal, ovoidal,oblong, or of any similar regular or non-regular geometric shape havingat least two rounded sides separated by a first axis and at least twosides separated by a second axis. In the preferred embodiment, the firstaxis (a major axis) is greater than the second axis (a minor axis).Sprockets having such design are termed, collectively, as being“oblongated”. Such specially designed sprockets are needed in order toprovide proper turning of the steerable wheels, to ensure the steerablewheels rotate during the turn instead of drag across the turf, and tokeep proper tension in the chains. This is possible because theoblongated sprockets provide an unmatched radius of rotation about thecenter of the drive wheel axis for one steerable front wheel withrespect to the other steerable front wheel. This provides anasynchronously steered system and is not possible with standard circularsprockets. Rotating the steering wheel in turn rotates the steeringshaft via one or more chains that meshingly engage the first and secondwheel sprockets. The oblongated wheel sprockets rotate the first andsecond steerable front wheels in a manner that provides true zero-radiusturning capability without ploughing or scraping the turf.

Thus, when the steering input is engaged in a particular direction, thesteering shaft rotates in a like fashion. That rotation is translated tothe wheel sprockets via one or more chains, causing the frontground-engaging wheels to pivot in an amount proportional to therotation of the steering device. Other structures such as belts, cables,and the like are also possible to translate the rotation from thesteering shaft to the ground-engaging wheels. Preferably, one or moreidler sprockets is pivotally attached to opposing sides of the framenear the front of the vehicle. One or more of the idler sprocketsmeshingly engages the left chain, while the other idler sprocketsmeshingly engage the right chain. One purpose of the idler sprockets maybe to tension the chain, assisting in the turning of the front wheels.Another purpose may be to provide a means to adjust the steering systemfor proper wheel alignment and function.

A drive wheel locomotion system is provided that links a forward input(e.g., a pedal) and a reverse input (e.g., a pedal) to each of theground-engaging drive wheels. The drive wheels are independently drivenby separate drive units connected to first and second hydrostatic pumps.Each pump has a pump arm that is connected to a swash plate internal tothe pump. The pump arms are rotatable in both a forward and a backwarddirection in amounts that correlate to varying speeds provided by theuser via the forward input and the reverse input.

A pump forward control assembly provides the linkage between the forwardinput and the pump arms to rotate the pump arms in a forward directionto drive the drive wheels forward. However, even though the drive wheelsare capable of being independently driven, the pump forward controlassembly links the forward input to the drive wheels in a combinedfashion. That is, the pump forward control assembly moves the pump armsin equal amounts. It does not, by itself, allow the forward input toindependently drive the drive wheels. The ability to drive the drivewheels independently is provided by a cam engagement system, describedbelow.

The reverse input is also linked to the pump forward control assembly,but in a manner such that movement of the reverse input rotates the pumparms of the first and second pumps in a backward direction. This has theeffect of driving the drive wheels in a reverse direction in equalamounts. The reverse input, similar to the forward input, cannot byitself drive one drive wheel at a different speed than the other drivewheel. The forward and reverse inputs may comprise forward and reversepedals, as described, but need not be separate pedals. In fact, theforward and reverse inputs may comprise a single pedal, lever, or othermechanism that moves in first and second directions.

As described, each drive unit may comprise a hydrostatic motor and ahydrostatic pump. Each hydrostatic motor may include an output shaftwhich is coupled with a first or second of the rear ground-engagingwheels, respectively, such that each rear wheel may be independentlydriven via the cam engagement system. In this manner, by allowing therear wheels to drive at different speeds relative to each other, thepresent invention possesses very tight cornering capability, and caneven achieve a zero radius turning. The ability to drive the drivewheels at different speeds relative to each other is linked to the frontwheel steering system via the cam engagement system.

The front wheel steering system, described above, steers the frontwheels in a first stage of steering. However, through the use of the camengagement system, the front wheel steering system also comprises asecond stage of steering that provides the ability to drive the drivewheels at different speeds with respect to each other.

In the second stage the steering wheel is coupled to the drive wheellocomotion system in a manner that allows the power applied to one orthe other of the rear wheels to be altered in response to steering inputwhen the vehicle is operated in a forward direction. Which of the drivewheels is slowed depends on the direction of steering input. Theengagement cam system comprises an engagement cam shaft that isrotatable forward from a first position via linkage to the forwardinput.

The engagement cam system further comprises at least one cam followerthat moves forward during rotation of the engagement cam shaft. The atleast one cam follower can also employ at least one bearing thereon forreceiving contact by a steering cam (described below). Again, however,for the sake of convenience, the description discusses a first camfollower having a first bearing thereon for meeting a first steeringcam, and a second cam follower having a second bearing thereon formeeting a second steering cam. This shall not be deemed to limit theinvention to requiring two cam followers, two bearings, and two steeringcams. The first and second cam followers further comprise first andsecond bearings that receive contact by first and second steering cams(described below). When the engagement cam shaft is rotatedsufficiently, this places the first and second bearings in position tomake independent contact with the first and second steering cams. Thefirst and second cam followers are independently rotatable in a rearwarddirection via the contact made by the first and second steering cams andthe first and second bearings, respectively. The first cam follower isconnected to the pump arm of the first pump (associated with the firstdrive wheel) via a first push cable. The second cam follower isconnected to the pump arm of the second pump (associated with the seconddrive wheel) via a second push cable. Again, the discussion of a firstand second push cable is for convenience. A single push cable could alsobe utilized.

In this second stage of steering, the steering shaft further comprises asteering cam shaft having thereon at least one steering cam. Again, forthe sake of convenience, the discussion describes a first and secondsteering cam. This shall not be deemed to limit the invention torequiring two steering cams. The first and second steering cams have aperimeter or a portion of a perimeter that increases in radius in agiven circumferential direction. A single steering cam embodiment wouldcontain portions of a perimeter that increase in radius in two givencircumferential directions. The rate of the increasing radius of theouter surface or perimeter of the steering cams can vary in anygenerally curvate relationship. The outer surface can contain portionsthat are spiral, parabolic, elliptical, or of any conic section or othercurvate noncircular geometry. The only requirement is that each pointalong the perimeter in a given circumferential direction is located at agreater distance than the previous point.

When the forward input is depressed, as stated, the linkage rotates theengagement cam shaft forward, which moves the first and second camfollowers forward such that the first and second bearings are now in areceiving position. In this receiving position, if the user provides asteering input, the steering cam shaft rotates. If the steering input isa left turn, the first steering cam begins to rotate about its axis ofrotation, and when it does it brings its increasing radius into contactwith the first bearing. As more steering input is applied, more of theincreasing radius of the first steering cam contacts the first bearing,forcing the first bearing and the first cam follower in an increasinglybackward direction. Because the first cam follower is connected to thefirst end of the first push cable, the backward direction of the camfollower provides a compressive force (a “push”) onto the pump arm ofthe first pump associated with the first (inside) drive wheel. This hasthe effect of slowing the inside drive wheel in proportion to the leftsteering input.

In similar fashion, if the steering input is a right turn, the secondsteering cam begins to rotate about its axis of rotation, and when itdoes it brings its increasing radius into contact with the secondbearing. As more steering input is applied, more of the increasingradius of the second steering cam contacts the second bearing, forcingthe second bearing and the second cam follower in an increasinglybackward direction. Because the second cam follower is connected to afirst end of the second push cable, the backward direction of the camfollower provides a compressive force (a “push”) onto the pump arm ofthe second pump associated with the second (inside) drive wheel. Thishas the effect of slowing the inside drive wheel in proportion to theright steering input.

In this embodiment, the reverse input is not connected to the first andsecond cam followers. This means that when the reverse input is engagedand the vehicle is operated in reverse, if the operator turns thesteering device, the rear wheel steering mechanism will not operate toalter the amount of power applied to either wheel. Therefore, when thereverse input is engaged and the vehicle is operated in reverse, thesteerable front wheels are the only means of steering the vehicle.

Optionally, the invention comprises an automatic self-catching seatlatch for use with or without roll-over protection systems (“ROPS”). Theincreasing use of ROPS systems provides additional safety features forthe operator of such vehicles. However, one requirement of ROPS systemsis the inclusion of a positive seat latch mechanism that locks the seatto the frame. Many varieties of seat latch systems are found in the art,but a majority of these systems utilize components welded directly to aseat mount or to the frame. The welded structure creates at least twosignificant problems. First, if the welds break, the entire seat mountmust be removed in order for the latch to be repaired or replaced. Thiscosts the user significant dollars and significant time to repair.Second, because of the welded structure, no adjustability is designedinto the latch. Therefore, upon lengthy use and normal wear and tear,the latch mechanisms may become less effective due to movement of thecomponents over time. An optional adjustable removable seat latch systemis provided in the preferred embodiment to eliminate these problems.

The adjustable removable seat latch system comprises at least a firstlatch having an activation portion and a catch portion. The latch ispivotable about a shaft that is preferably spring-loaded into a “latch”position. The catch portion further comprises an angled section oppositethe activation portion, a groove for engaging a sturdy portion of thevehicle (for example, the frame), and an adjustment block foradjustability in horizontal and vertical directions. To expose theunderside of the seat, the user depresses the activation portion,rotating it against the spring force to move the groove out of aninterlocking relationship with the sturdy portion of the vehicle. Toclose the seat, the user simply lets the seat drop, which brings theangled section of the latch into engagement with the sturdy portion ofthe vehicle. As the seat continues to move downward under its ownweight, the angled section continues to move along the sturdy portion ofthe vehicle, and the latch begins to rotate against the spring force. Asthe seat reaches its final destination, it brings the groove intointerlocking engagement with the sturdy portion of the vehicle, and thespring snaps into locking position. The seat is now automaticallylocked. Adjustability is provided with the adjustment block.

Optionally, the apparatus can also include a cruise control system toallow the user to remove his/her foot from the forward pedal, therebyreducing user fatigue during long mowing operations. The cruise controlsystem comprises a cruise control shaft having a cruise control linkoperatively connected to a handle. The cruise control link connects tothe forward control shaft that in turn connects to the pump forwardcontrol assembly. Thus, when the user moves the handle to engage thecruise control system, the cruise control shaft rotates the cruisecontrol link into engagement with the forward control shaft, which movesthe pump forward control assembly forward, moving the pump arms of thepumps forward in an equal amount. A catch is provided for the handle sothat the user can select and maintain the desired amount of ground speedfor the cruise control.

The present invention therefore provides a ZTR vehicle having a meansfor steering at least one steerable front wheel; a means for couplingthe independent drive wheels for driving at equal speeds and directions;and a means for selectively de-coupling the independent drive wheels inorder to drive them at unequal speeds and/or unequal directions.

The present invention further provides a two-stage steering assembly fora zero-turn radius vehicle having at least one steerable front wheeloperatively coupled to a steering input and at least two independentlydriven drive wheels, wherein the two-stage steering assembly furthercomprises at least one steering cam operatively coupled to the steeringinput. The at least one steering cam further comprises a surface forselectively coupling with at least one cam follower, wherein the atleast one cam follower is coupled with the at least two independentlydriven drive wheels for providing unequal locomotive power to the atleast two independently driven drive wheels. At least one oblongatedwheel sprocket is operatively connected to the steering input and to theat least one steerable front wheel for translating the steering inputinto a steering direction of the at least one steerable front wheel.

The present invention further provides a method for separating asteering input of a vehicle having independently driven drive wheelsinto a front wheel steering system and a drive wheel bias system. Themethod comprises providing at least one wheel sprocket operativelyconnecting the steering input to at least one steerable front wheel andproviding at least one steering cam that selectively couples thesteering input to a pump mechanism of the drive wheel bias system toprovide bias to the independently driven drive wheels of the vehicle viaa forward input for delivering forward locomotive power to the drivewheel bias system.

The invention further provides a steering cam assembly comprising atleast one steering cam rotatably mounted to a steering cam shaft about afirst axis of rotation. The steering cam shaft is operatively connectedto a steering input, wherein the at least one steering cam furthercomprises at least a portion of a perimeter disposed noncircularly aboutsaid first axis of rotation.

The invention also provides an oblongated sprocket for steering at leastone front wheel of a multistage steering vehicle. The oblongatedsprocket comprises at least two convex curved sides oppositely disposedseparated by a first distance and at least two sides connecting the atleast two convex curved sides separated by a second distance, whereinthe first distance is greater than the second distance.

The invention further provides an engagement cam system for a vehiclewith a multistage steering system comprising an engagement cam coupledto an engagement cam shaft rotatably connected to the vehicle. At leastone steering cam is rotatably mounted to said vehicle and coupled to asteering device for receiving a steering input. At least one camfollower is coupled to the engagement cam shaft and moveable from afirst nonengaging position wherein contact cannot occur between the atleast one steering cam and the at least one cam follower, to a secondengaging position wherein contact can occur between the at least onesteering cam and the at least one cam follower. A forward control shaftis operatively connected to a forward input and rotatable by the forwardinput, and the forward input further engages the engagement cam to movethe at least one cam follower from the first nonengaging position to thesecond engaging position.

Furthermore, a cruise control system is provided for a zero turn radiusvehicle with steerable front wheels and independently driven drivewheels. The cruise control system comprises a cruise control linkoperatively coupled to a forward control mechanism providing power tothe independently driven drive wheels in response to a forward input Alever is rotatably mounted to the vehicle and movable from a firstnonengaging position to at least one engaging position. A catchmechanism is engageable with the lever for maintaining a selectedposition of the lever, wherein when the catch mechanism engages thelever when it is in the at least one engaging position, the forwardcontrol mechanism continues to provide power to the independently drivendrive wheels at a constant rate.

And, the invention provides an adjustable removable seat latch systemcomprising a latch coupled to a removable adjustment device. The latchfurther comprises an activation portion rotatably disposed oppositelyfrom a catch portion. The catch portion further comprises an angledsection terminating in a locking surface wherein the latch is biased ina position wherein the locking surface engages a structure external tothe latch, and wherein the removable adjustment device comprisesadjustment means for adjustability in at least one dimension.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can take many physical embodiments and can assumemany arrangements of components for carrying out the teachings of theinvention, all of which may be appreciated by a person of skill in theart. The teachings of the present invention can be readily understood byconsidering the following detailed description of a preferred embodimentin conjunction with the accompanying drawings of said embodiment, inwhich:

FIG. 1 is a perspective view of an apparatus according to a preferredembodiment in the form of a zero-turn radius lawn mower;

FIG. 2 is a top view shown slightly in perspective of the apparatusshown in FIG. 1;

FIG. 3 is a left side elevation view of the apparatus shown in FIG. 1;

FIG. 4 is a right side elevation view of the apparatus shown in FIG. 1;

FIG. 5 is a front elevation view of the apparatus shown in FIG. 1;

FIG. 6 is a control panel for a vehicle according to a preferredembodiment;

FIG. 7 is a schematic of a front wheel steering system according to apreferred embodiment, shown when the steering input is zero;

FIG. 8 is a schematic of the front wheel steering system shown in FIG.6, shown when the steering input is high, indicating a right zero-radiusturn;

FIG. 9 is close-up schematic of the front wheel steering system shown inFIG. 8;

FIG. 10 is a top plan view of a first or second oblongated wheelsprocket according to a preferred embodiment;

FIG. 11 is top view of the major linkages and systems of a vehicleaccording to a preferred embodiment;

FIG. 12 is a perspective view of the forward control shaft linkage andthe engagement cam shaft linkage of a vehicle according to a preferredembodiment;

FIG. 13 is top view of the forward control shaft linkage and theengagement cam shaft linkage shown in FIG. 12;

FIG. 14A is a perspective view of the engagement cam shaft linkage of avehicle according to a preferred embodiment shown when the forward inputhas been depressed enough to bring the engagement cam roller intocontact with the first surface of the engagement cam;

FIG. 14B is a perspective view of the engagement cam shaft linkage ofFIG. 14A shown after additional forward input moving the engagement camroller to the second surface of the engagement cam, indicating rotationof the engagement cam shaft and movement of the gusset plate;

FIG. 14C is a perspective view of the engagement cam shaft linkage ofFIG. 14B shown after additional forward input, indicating no additionalrotation of the engagement cam shaft and no additional movement of thegusset plate;

FIG. 15 is a perspective view of the reverse input linkage of a vehicleaccording to a preferred embodiment;

FIG. 16 is a top view of the reverse input linkage shown in FIG. 15;

FIG. 17 is a perspective view of the gusset plate and cam followersaccording to the preferred embodiment;

FIG. 18 is a front partial perspective view of a portion of the steeringsystem according to a preferred embodiment, showing a part of a steeringshaft and a portion of a steering cam shaft, joined by a universaljoint;

FIG. 19 is a partial right side elevation view of a steering systemaccording to a preferred embodiment shown with no steering input;

FIG. 20 is a plan view of a portion of an engagement cam systemaccording to a preferred embodiment, showing a steering input of zeroand showing the first and second cam followers in a forward receivingposition to receive contact from the first or second steering cams;

FIG. 21 is a partial right side elevation view of steering system shownin FIG. 19 shown during a high steering input indicating a zero-radiusright turn;

FIG. 22 is a top view of a portion of an engagement cam system as shownin FIG. 20 where a steering input indicating a right turn has been made,forcing the second bearing backward;

FIG. 23 is a partial left side elevation view of a steering systemaccording to a preferred embodiment shown during a high steering inputindicating a zero-radius left turn;

FIG. 24 is a top view of a portion of an engagement cam system as shownin FIG. 20 where a steering input indicating a left turn has been made,forcing the first bearing backward;

FIG. 25 is a perspective view of the pump forward control assembly of avehicle according to the preferred embodiment showing the vehicle inneutral and showing no steering input;

FIG. 26 is a perspective view of the pump forward control assembly shownin FIG. 25 where a reverse input has been made indicating the vehicle isin reverse;

FIG. 27 is a top view of the pump forward control assembly shown in FIG.26;

FIG. 28 is a perspective view of the pump forward control assembly shownin FIG. 25 where a forward input has been made indicating the vehicle isin moving straight forward, with no steering input;

FIG. 29 is a perspective view of the pump forward control assembly shownin FIG. 28 where a steering input has been made indicating a left turn;

FIG. 30 is a perspective view of the pump forward control assembly shownin FIG. 29 where a high left steering input has been made indicating azero-radius turn in a counterclockwise direction;

FIG. 31 is a perspective view of the pump forward control assembly shownin FIG. 28 where a steering input has been made indicating a right turn;

FIG. 32 is a perspective view of an adjustable removable seat latchsystem according to a preferred embodiment showing the seat in an openposition;

FIG. 33 is a perspective view of an adjustable removable seat latchsystem shown in FIG. 32 showing the seat in an closed position showingthe latch in a locked position;

FIG. 34 is a perspective view of an adjustable removable seat latchsystem shown in FIG. 32 showing the seat in a closed position butshowing the latch in an unlocked position;

FIG. 35 is a left perspective view of a cruise control system accordingto a preferred embodiment;

FIG. 36 is a right side view of the cruise control system of FIG. 35;and

FIG. 37 is a side view of an automatic height adjustment means for amowing deck according to a preferred embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

While the present invention will be described more fully hereinafterwith reference to the accompanying drawings in which particularembodiments and methods are shown, it is to be understood from theoutset that persons of ordinary skill in the art may modify theinvention herein described while achieving the functions and results ofthis invention. Sound engineering judgment may be used to modify variousaspects and components of the invention without detracting from thebroad, general teachings hereof. Accordingly, the description thatfollows is to be understood as illustrative and exemplary of specificembodiments within the broad scope of the present invention and not aslimiting the scope of the invention. In the following descriptions, likenumbers refer to similar features or like elements throughout.

FIGS. 1 through 37 depict an apparatus 10 in the form of a vehicleaccording to one embodiment of the invention. Throughout thisdescription the terms “apparatus” and “vehicle” will be usedinterchangeably. Referring first to FIGS. 1 through 6 generally, theapparatus 10 generally comprises a frame 11 to which is connected to atleast one steerable front wheel, but preferably to first and secondsteerable front wheels 20, 30 and first and second drive wheels 40, 50.An engine 12 is mounted on the frame 11 to provide power for theapparatus 10. Obviously the engine 12 can be an internal combustionengine, a diesel engine, or any other form of engine known in the artfor providing adequate power to vehicles of this sort. Preferably a seat13 is also mounted on the frame 11, via a seat mount 13 a to provideseating for the user. A steering device 61 is also mounted on the frame11 to allow the user to provide steering inputs to the apparatus 10.Likewise, a forward input 70 and a reverse input 80 are also shown andare provided in a convenient location for the user. In the embodimentshown, the forward input 70 comprises a pedal 71 and the reverse input80 comprises a reverse pedal 81, but obviously other configurations arepossible (a single pedal, levers, sticks, joysticks, and so forth).Because a preferred embodiment of the apparatus 10 is in the form of alawnmower, a mowing deck 14 is also shown, and a control panel 18 isshown in FIG. 6.

Referring generally to FIGS. 14 and 17 through 31, the apparatus 10provides a multistage steering input to both steer the first and secondsteerable front wheels 20, 30 and to selectively engage a drive wheellocomotion system 700 in a manner that slows the speed of the insidedrive wheel. The multistage steering of the apparatus 10 does not linkevery steering input to the drive wheel locomotion system. Rather, withthe use of an engagement cam system 740 (to be described later), thesteering of the apparatus 10 is bifurcated into two separate types ofsteering results. However, before this multistage steering is described,a description of the means for locomotion is described.

In general, a drive wheel locomotion system 700 is used to providemobility for the vehicle in both forward and reverse directions. Thefollowing description of one embodiment of the drive wheel locomotionsystem 700 in a forward direction will discuss specific components of apreferred system with reference numerals beginning with the digits 4, 5,7, and 9. It should be understood, however, that this description is notmeant to limit in any way the overall system; rather, it is used todescribe the embodiment shown in sufficient detail for a completeunderstanding.

Referring now to FIGS. 7, 8, 11, and 13, an independent drive unit isconnected to each of the first and second drive wheels 40, 50. A firstdrive unit 41 is connected to the first drive wheel 40, while a seconddrive unit 51 is connected to the second drive wheel 50. In the depictedembodiment, the first drive unit 41 comprises a first hydrostatic pump42 and the second drive unit 51 comprises a second hydrostatic pump 52.Other drive units 41, 51, as the means for driving the apparatus 10, arepossible, including transmissions, electric drive units, belt driveunits, and so forth. In the depicted embodiment, the means for drivingthe apparatus 10 are the first and second hydrostatic pumps 42, 52 andtheir associated motors, hydraulic reservoirs, and hoses. These pumps42, 52 may be any of a number of known types and styles of hydrostaticpumps, in particular pumps manufactured by Hydrogear. To list but a few,Hydrogear BDP-10, BDP-12, BDP-16, BDP-20, and BDP-24 work well in theinvention, with BDP-10, BDP-12, and BDP-16 pumps being preferred,depending on the size of the vehicle 10. The pumps 42, 52 include pumpshafts 43, 53 for connection (via pulley or similar means) to the engine12 for power.

The drive units 41, 51 of the depicted embodiment further comprise afirst drive motor 44 and a second drive motor 54, which are operated bythe first and second hydrostatic pumps 42, 52, respectively. The firstdrive motor 44 is connected to the first drive wheel 40 via an outputshaft 45. The second drive motor 54 is connected to the second drivewheel 50 via an output shaft 55. The first hydrostatic pump 42 includesa pump arm 46. The pump arm 46 is rotatably connected to the firsthydrostatic pump 42 on an axis of rotation 46 a Connected to the pumparm 46 and internal to the pump 42 is a swash plate 47 (not shown).Swash plate 47 regulates the amount and direction of power delivered bythe first drive unit 41 to the first drive wheel 40 via output shaft 45.When the pump arm 46 is rotated about its axis of rotation 46 a, theswash plate 47 likewise rotates inside the first hydrostatic pump 42 tocontrol fluid flow. Pump arm 46 can be rotated in a forward (clockwisewhen viewing the vehicle 10 as shown in FIG. 4) or a backward(counterclockwise when viewing the vehicle 10 as shown in FIG. 4)direction. Throughout this discussion the terms “forward” and “backward”or “rearward” refer to the directions associated with the vehicle 10shown in the figures, where “forward” would normally be associated witha direction toward the front of the vehicle 10, and “backward” wouldnormally be associated with a direction toward the back of the vehicle10.

As will be discussed below, the pump arm 46 may be rotated about itsaxis of rotation 46 a forward or backward in response to operator input.When the pump arm 46 is rotated forward, it causes the swash plate 47 torotate forward, which in turn causes power to be applied to the firstdrive wheel 40 in the forward direction in an amount proportional to theamount of forward input applied by the operator. When the pump arm 46 ismoved in a rearward direction, the swash plate 47 is moved in a rearwarddirection, causing power to be applied to the first drive wheel 40 inthe reverse direction.

In like manner, second hydrostatic pump 52 includes a pump arm 56, anaxis of rotation 56 z, and a swash plate 57, and operates in the samemanner as the above-described first hydrostatic pump 42. In this manner,the speeds of the first drive wheel 40 and the second drive wheel 50 maybe independently manipulated to achieve zero radius turning. A pumpforward control assembly 480 connects a forward pedal 71 to the pumparms 46, 56 (see below for further discussion) such that when theforward pedal 71 is activated, both pump arms 46, 56 rotate forward inequivalent amounts.

When neither forward nor reverse input is being applied by the operatorvia the forward input 70 or reverse input 80, the pump arms 46, 56 andswash plates 47, 57 rest in a neutral position and no output is appliedto the drive wheels 40, 50 by the drive motors 44, 54. In the depictedembodiment, a biasing means (not related to the defined term “bias” setforth above in relation to the differing speeds of the drive wheels) isused to return the system to a neutral position, wherein the apparatus10 is at rest. The biasing means of the depicted embodiment comprises afirst spring 90 having a first end 90 a connected to a forward controlshaft 712 (described below) and a second end 90 b connected to the frame11. Preferably a second spring 91 having a first end 91 a connected to agusset plate 765 and a second end 91 b connected to the frame 11 is alsoprovided to ensure a safe and quick return to neutral. Pump controlsprings 483, 484 are also provided to assist the vehicle in findingneutral. Magnetic sensing proximity switches 486 are also provided insatisfaction of ANSI-B71.4 safety standard that requires switches thatsense neutral. This prevents the vehicle 10 from being started if not inneutral.

Although the details of each of these components will follow, at thispoint a general understanding of the main shafts of the vehicle 10 isinstructive. In general, referring to FIG. 11, three separate rotatingshafts are provided. FIGS. 12 and 13 show a forward control shaft 712and its associated preferred linkages. FIGS. 14A, 14B, and 14C show anengagement cam shaft 742 and its associated preferred linkages. FIGS. 15and 16 show a reverse linkage shaft 84 and its associated preferredlinkages. The forward control shaft 712 connects a forward input to thepump forward control assembly 480 to rotate the pump arms 46, 56 in aforward direction equally. The reverse linkage shaft 84 connects areverse input to the pump arms 46, 56 in a manner that rotates the pumparms 46, 56 in a backward direction, equally. The engagement cam shaft742 connects to the forward input via an engagement cam 741 to first andsecond cam followers 750, 755 that move first and second bearings 780,790 into a position in which the bearings 780, 790 can be contacted byfirst and second steering cams 681, 691, respectively.

Now that some of the general structures associated with the drive wheellocomotion system 700 have been described, attention will be turned toadditional preferred structures used to operate the drive wheels 40, 50.In general, the following discussion describes a drive wheel locomotionsystem 700 according to the depicted embodiment. Referring again toFIGS. 11 through 14, forward pedal 71 is rotatably connected to aforward pedal pivot 710. A first forward link 711 having a first end 711a and a second end 711 b is connected at its first end 711 a to theforward pedal pivot 710. The second end 711 b of the first forward link711 is connected to a forward control shaft 712 via an arm 713. Theforward control shaft 712 is rotatably connected to the frame 11 andfurther comprises a tab 714 extending therefrom. As will be describedagain later, forward movement of the first forward link 711 brings arm713 into engagement with tab 714, and further forward movement thenrotates forward control shaft 712.

A second forward link 715 is connected at its first end 715 a to an arm716 connected to the forward control shaft 712. A second end 715 b ofthe second forward link 715 is connected to the pump forward controlassembly 480. The pump forward control assembly 480 is preferably awelded assembly having a pivot or axis of rotation 480 c located on thesame axis of rotation 46 a, 56 a as the pump arms 46, 56 and for theswash plates 47, 57. In fact, the pump arms 46, 56 are directlyconnected to the pump forward control assembly 480 via forward controlassembly link 481 such that movement of the pump forward controlassembly 480 rotates the pump arms 46, 56. A contact plate 482 providesa rest position for pump arms 46, 56 such that when pump forward controlassembly 480 is rotated forward, pump arms 46, 56 maintain their restposition at contact plate 482. In this manner, forward movement of thesecond forward link 715 rotates both pump arms 46, 56 equally about theaxis of rotation 46 a, 56 a, causing drive wheels 40, 50 to rotate atequal speeds, causing straight forward motion of the vehicle 10.

A first push cable 760, having a first end 760 a and a second end 760 b,and a second push cable 770, having a first end 770 a and a second end770 b are also provided. The first ends 760 a, 770 a of the push cables760, 770 are connected, respectively, to the first and second camfollowers 750, 755. The second ends 760 b, 770 b of the first and secondpush cables 760, 770 are connected, respectively, to the pump arms 46,56 via the pump forward control assembly 480. The first and second pushcables 760, 770 are connected to the pump forward control assembly 480in such a manner that they can move forward together, but their secondends 760 b, 770 b can move backward independently. When they moveforward, the pump forward control assembly 480 provides the forwardmovement to the pump arms 46, 56 in equal amounts. However, when thefirst and second push cables 760, 770 move backward, they canindependently push the push arms 46, 56, respectively. In this manner,the first and second push cables 760, 770 provide a compression linkbetween the pump arms 46, 56 and the first and second cam followers 750,755, respectively.

Referring now to FIGS. 11 through 13 and 17, a gusset plate 765 providesthe main rotatable mount for the housing 760 c of the first push cable760 and for the housing 770 c of the second push cable 770. The gussetplate 765 has a first end 765 a and a second end 765 b. The first end765 a is pivotally connected to the frame 11. The second end 765 bfurther comprises a gusset plate link 766 directly connecting the gussetplate 765 to the engagement cam shaft 742. In this manner, forwardrotation of the engagement cam shaft 742 results in forward rotation ofthe gusset plate 765, and thus results in forward rotation of the firstand second cam followers 750, 755 via gusset link 766. This movement isshown in FIGS. 14A and 14B.

Referring to FIGS. 11, 13 and 25, note that the pump forward controlassembly 480 always moves the pump arms 46, 56 forward in equal amounts,as a result of forward control assembly link 481. In this manner,depressing the forward pedal 71 does not, by itself, perform any turningof the vehicle 10. This is true because simply depressing the forwardpedal 71 provides no ability to move the pump arms 46, 56 independentlyof each other. In this manner, the engagement cam shaft 742 can berotated by pressing the pedal 71, thereby moving the first forward link711 forward, which in turn moves the second forward link 715 forward,which in turn rotates the pump forward control assembly 480, thusrotating the pump arms 46, 56 and the swash plates 47, 57 in equalamounts.

Now that the overall operation of the means for locomotion has beendescribed, attention turns to the multistage steering capabilities ofthe apparatus 10. As stated, the vehicle 10 of the depicted embodimentcan provide, selectively, steering input in two stages. These stages canoccur simultaneously. First, the steering input directly controls afront wheel steering system 600 to directly steer the first and secondsteerable front wheels 20, 30. Second, the steering input, depending onthe speed and the direction of the vehicle 10, contains a unique systemfor selectively engaging the drive wheel locomotion system 700(described above) in a manner that allows the inside drive wheel 40, 50(depending on the direction of the steering input) to be slowed.Importantly, not all steering inputs automatically engage the drivewheel locomotion system 700 to alter the speed of one drive wheel 40, 50with respect to the other. It will be beneficial to first provide adiscussion of the front wheel steering system 600.

Referring again to FIGS. 7 through 10, the front wheel steering system600 includes a steering device 61 (in this embodiment the steeringdevice 61 is a steering wheel 62). The steering wheel 62 is mechanicallyconnected to the first and second steerable front wheels 20, 30. Itshould be noted that while mechanical steering linkage is herein furtherdescribed, any form of steering linkage that can translate a steeringinput from the steering wheel 62 to a steering cam shaft 680 (describedbelow) may be possible as known in the art to achieve the intendedfunctions described herein. For example, the mechanical steering system600 may include a hydraulic steering system with its associated pumpsand connections in known fashion. Because this embodiment usesmechanical linkages, only the mechanical system will be furtherdescribed.

Referring additionally to FIGS. 18, 19, 21, and 23 The steering wheel 62is connected to a first steering wheel shaft 63 at the end of which is afirst sprocket 64. It can be seen that the first steering wheel shaft 63is typically disposed at an angle relative to vertical. A secondsteering wheel shaft 65, having first and second ends 65 a, 65 b,respectively, comprises a second sprocket 66 attached at the first end65 a The second end 65 b is connected to a first end 67 a of a universaljoint 67 (having a first end 67 a and a second end 67 b). This universaljoint 67 translates the rotation of the angled second steering wheelshaft 65 to a rotation about a vertical axis. A chain 69 meshinglyengages the teeth of the first and second sprockets 64, 66. The firstand second sprockets 64, 66 are preferably selected in such a manner asto provide a gear reduction: that is, sprocket 66 has a larger diameterthan that of second sprocket 64. This reduces the turning force neededto turn the wheels 20, 30. It should be noted that, as stated, manyembodiments of the steering linkage are possible, including direct driveconnections without gear reduction.

With continuing reference to FIGS. 18, 19, 21, and 23, a steering camshaft 680 is connected to the second end 67 b of the universal joint 67.The steering cam shaft 680 has a first end 680 a (connected to thesecond end 67 b of the universal joint 67) and a second end 680 b and anaxis of rotation 680 c about which the steering cam shaft 680 rotates.In this embodiment a third sprocket 640 and a fourth sprocket 650 aremounted at the second end 680 b of the steering cam shaft 680. The thirdsprocket 640 receives chain 641 for engaging a first wheel sprocket 21.Similarly, the fourth sprocket 650 receives chain 651 for engaging asecond wheel sprocket 31. Obviously it is recognized that a singlesprocket and a single chain could be used in place of the third andfourth sprockets 640, 650 and chains 641, 651.

The first and second steerable front wheels 20, 30 are rotatably mountedabout a horizontal axis to first and second wheel yokes 20 a, 30 a,respectively. The wheel yokes 20 a, 30 a are in turn rotationallymounted about a vertical axis to the frame 11 via first and secondcaster pivot mounts 20 b, 30 b. First and second wheel sprockets 21, 31are mounted, respectively, to the first and second caster pivot mounts20 b, 30 b. In this arrangement, a steering input at the steering wheel62 rotates first and second sprockets 64, 66 via chain 69, which in turnrotates the universal joint 67. This in turn rotates third sprocket 640which rotates first wheel sprocket 21 via chain 641, and fourth sprocket650 which rotates second wheel sprocket 31 via chain 651.

Referring again to FIGS. 7 through 9, in this embodiment one or moreidler sprockets 660 may be mounted to the frame 11 to provide tension tothe chains 641, 651 (perhaps via spring mounts), or, alternatively, toprovide adjustment means for proper alignment of the first and secondfront steerable wheels 20, 30. In this embodiment, idler sprockets 660are pivotally mounted to the frame 11 via idler sprocket brackets 661.An idler sprocket adjustment device 662 is shown in the figures as athreaded adjustment, but many known means of adjustment for such devicesare possible.

Referring now to FIGS. 7 through 9 and to FIG. 10, the first and secondwheel sprockets 21, 31 will be further described. The first wheelsprocket 21 is preferably noncircular, having a first axis 22 and asecond axis 23. Many regular geometric shapes other than that shown inthe figures are possible for the first wheel sprocket, including,without limitation, oblong, ovoidal, ellipsoidal, and so forth. Othernon-regular geometric shapes are also possible, for example asubstantially “I-shaped” member having curved ends separated by aconnector. Likewise, a substantially “H-shaped” member having curvedends separated by more than one connector are possible, and so forth.The goal being to provide a sprocket with an outer perimeter 24 havingat least two curved portions 25, 26 oppositely disposed, separated by adistance. All such designs shall be generically referred to as“oblongated”. In the oblongated embodiment shown in the figures, thefirst wheel sprocket 21 is basically a rectangular member having twocurved ends 25, 26 separated by a first axis 22 (a major axis) that isgreater than the second axis 23 (a minor axis).

In similar fashion, second wheel sprocket 31 is preferably noncircular,having a first axis 32 and a second axis 33. Many regular geometricshapes other than that shown in the figures are possible for the firstwheel sprocket, including, without limitation, oblong, ovoidal,ellipsoidal, and so forth. Other non regular geometric shapes are alsopossible, for example a substantially “I-shape” member having curvedends separated by a connector. Likewise, a substantially “H-shaped”member having curved ends separated by more than one connector arepossible, and so forth. The goal being to provide a sprocket with anouter perimeter 34 having at least two curved portions 35, 36 oppositelydisposed, separated by a distance. All such designs shall be genericallyreferred to as “oblongated”. In the oblongated embodiment shown in thefigures, the second wheel sprocket 31 is basically a rectangular memberhaving two curved ends 35, 36 separated by a first axis 32 (a majoraxis) that is greater than the second axis 33 (a minor axis).

Using an oblongated sprocket design allows the vehicle 10 to achieveproper turning and to have proper alignment during all directions oftravel. It allows the vehicle 10 to properly perform zero-radius turnswithout having one or both wheels “plough” or scrape the turf. This ispossible with a proper orientation of the first and second wheelsprockets 21, 31. When the wheels 20, 30 are not turned at all (that is,when the steering input is zero), the major axes 22, 32 are oriented sothat they intersect at the midpoint of the drive axle (labeled “P” inFIGS. 7 and 8).

Thus, when the steering wheel 62 is rotated in a clockwise orcounterclockwise direction, the first and second wheel sprockets 21, 31rotate accordingly. The chains 641, 651 translate the rotation of thesteering wheel 62 to the first and second wheel sprockets 21, 31,respectively, causing the wheel yokes 20 a, 30 a to pivot in an amountrelative to the rotation of the steering wheel 62. This causes the firstand second steerable front wheels 20, 30 to turn at an angle relative tothe rotation of the steering wheel 62.

In this embodiment, a mechanical stop 20 c, 30 c prevents the wheels 20,30 from rotating too far. Because the vehicle 10 can perform zero-radiusturns, the wheels 20, 30 are each capable of turning more than 90degrees in the direction of their respective turn. In other words, ifthe first steerable front wheel 20 is a left front wheel, it needs to becapable of turning more than 90 degrees from the longitudinal axis ofthe vehicle 10 in a left turn. Likewise, if the second steerable frontwheel 30 is a right front wheel, it must be capable of turning more than90 degrees from the longitudinal axis of the vehicle 10 in a right turn.This is preferred in order to keep the steerable front wheels 20, 30rotating in the turn and prevent them ploughing or scraping of the turf.Specifically, the preferred range of rotation for the first wheel 20(considering a counterclockwise rotation to be positive) isapproximately +108 degrees to approximately −72 degrees. Similarly, thepreferred range of rotation for the second wheel 30 is approximately +72degrees to approximately −108 degrees. With this geometry a zero-radiusturn is performed without having either wheel 20, 30 plough or scrapethe turf. Naturally, the degree of rotation allowed is dependent onvarious factors, including the size of the vehicle 10, the shape,alignment, and orientation of the first and second wheel sprockets 21,31, and the position of the caster pivot mounts 20 b, 30 b with respectto the wheels 20, 30. Given these variables, it is conceivable that therange of rotation described above could be altered by +/−30 degrees oreven more. So long as each wheel 20, 30 is angled at a tangent to itsradius of rotation (shown at Point “P” in FIGS. 7 and 8), the propergeometry is achieved.

In this embodiment, it is seen that the wheels 20, 30 are rotated abouta caster pivot 20 b, 30 b, respectively, that is located inwardly fromthe center of the wheels 20, 30. This allows lower turning forces tosteer the wheels 20, 30. Also, by locating the wheels 20, 30 outboard ofthe frame 11, the tendency of the wheels 20, 30 to tear the turf whilesteering the vehicle at low speeds is significantly reduced incomparison to vehicles on which the front wheels are located onboard theframe.

To reiterate, the steering system provides a multistage steering input.This means that the steering can occur at the front wheels 20, 30 or atboth the front wheels 20, 30 and the drive wheels 40, 50. Contrary toknown ZTR vehicles, steering of the vehicle 10 cannot occur only at thedrive wheels 40, 50. The front wheel steering system 600 used to steerthe steerable front wheels 20, 30 has just been described. Now attentionwill be turned to the system and mechanisms responsible for the secondstage steering input.

Referring again generally to FIGS. 11–14 and 17–24, an engagement camsystem 740 provides the mechanism whereby the steering device 61 canbehave in a multistage fashion. An arm 720 is mounted to forward pedalpivot 710. The arm 720 includes an engagement cam roller 730. Anengagement cam 741 is mounted to an engagement cam shaft 742. Theengagement cam 741 comprises a first surface 741 a and a second surface741 b (see FIGS. 12, 14A, 14B, and 14C). Preferably the second surface741 b is disposed at an angle (from vertical) in the forward directionwith respect to the first surface 741 a As discussed above, when theforward pedal 71 is depressed, it rotates forward pedal pivot 710 andmoves first forward link 711 forward. This rotates forward control shaft712 forward via arm 713 and tab 714 to provide forward power to thedrive wheels 40, 50 via second forward link 715. However, when theforward pedal 71 is depressed, it also rotates the engagement cam shaft742 forward. This is accomplished by the arm 720 and the engagement camroller 730. Arm 720 is connected to the forward pedal pivot 710. Thismovement is shown in FIGS. 14A, 14B, and 14C. FIG. 14A shows thesituation when the forward pedal 71 has been slightly depressed to bringthe engagement cam roller 730 into contact with the first surface 741 aof the engagement cam 741. Once this occurs, any additional activationof the forward pedal 71 results in rotation of the engagement cam shaft742 because the engagement cam roller 730 moves along the first surface741 a of the engagement cam 741 (see FIG. 14B). Once the engagement camroller 730 reaches the junction of the first surface 941 a and thesecond surface 941 b of the engagement cam 941, additional activation ofthe forward pedal 71 (see FIG. 14C) does not further rotate theengagement cam shaft 742. Rather, it merely results in increased groundspeed. When the forward pedal 71 is depressed, this rotates arm 720forward, which makes engagement cam roller 730 move along the firstsurface 741 a and the second surface 741 b of the engagement cam. Thepurpose of the angle between the first surface 741 a and the secondsurface 741 b is to provide a relief point wherein once the engagementcam roller 730 begins movement along the second surface 741 b, nofurther rotation of the engagement cam shaft 742 occurs. This will bedescribed below.

Referring now to FIG. 11 in conjunction with FIGS. 17–24, a first camfollower 750 having a first end 750 a and a second end 750 b ispivotally mounted at its first end 750 a to the frame 11. Similarly asecond cam follower 755 having a first end 755 a and a second end 755 bis pivotally mounted at its first end 755 a to the frame 11 at the samelocation as first cam follower 750. A first bearing 780 is movablymounted to the first cam follower 750 and a second bearing 790 ismovably mounted to the second cam follower 755. The first and second camfollowers 750, 755 and the first and second bearings 780, 790 serve toselectively and independently link the steering device 61 to the drivewheel locomotion system 700, as will be described in greater detailbelow.

Referring now to FIGS. 17 and 25–31, it is seen that the first andsecond push cables 760, 770 have their housings 760 c, 770 c connectedto the gusset plate 765. The first ends 760 a, 770 a of the first andsecond push cables 760, 770 are connected to the first and second camfollowers, 750, 755, respectively. Preferably, a spring 762 is mountedbetween the gusset plate 765 and the second end 760 b of the first pushcable 760 to keep a biasing force between the gusset plate 765 and thefirst cam follower 750. Similarly, a spring 772 is mounted between thegusset plate 765 and the second end 770 b of the second push cable 770to keep a biasing force between the gusset plate 765 and the second camfollower 755.

Depressing the forward pedal 71, as described above, rotates both theforward control shaft 712 and the engagement cam shaft 742, via thevarious components described (see FIG. 11). Because the gusset platelink 766 directly connects the gusset plate 765 to the engagement camshaft 742, rotation of the engagement can shaft 742 also rotates thegusset plate 765 to a forward position. In this forward position thefirst and second cam followers 750, 755 are brought into a positionwhere they can independently receive, in surface contact relationship,the first and second steering cams 681, 691, respectively.

Referring generally to FIGS. 17–24, the first steering cam 681 ismounted on a first portion of the steering cam shaft 680. The secondsteering cam 691 is mounted on a second portion of the steering camshaft 680. Both the first steering can 681 and the second steering cam691 are preferably, but not necessarily, disk-like in nature, having arelatively planar disk-like shape. Each steering cam 681, 691 comprisesan outer perimeter or at least a portion of an outer perimeter thatdefines a surface 682, 692 having a rotationally increasing radius fromthe center 680 a of the steering cam shaft 680. The surface 682, 692 ispreferably akin to a spiral where each point along the perimeter islocated farther away from the center 680 a than a previous point.Specifically, the first steering cam 681 is mounted on steering camshaft 680 so that a counterclockwise rotation of the steering wheel 62(indicating a left steering input) rotates an increasing radius of theouter surface 682 into increasing engagement with the first bearing 780.As this occurs, first bearing 780 and first cam follower 750 begin tomove backwards, thus causing first push cable 760 to push the pump arm46 in a rearward direction. This slows the speed of the first drivewheel 40, which is the inside wheel in a left steering input.

Similarly, the second steering cam 691 is mounted on steering cam shaft680 so that a clockwise rotation of the steering wheel 62 (indicating aright steering input) rotates an increasing radius of the outer surface692 into increasing engagement with the second bearing 790. As thisoccurs, second bearing 790 and second cam follower 755 begin to movebackwards, thus causing second push cable 770 to push the pump arm 56 ina rearward direction. This slows the speed of the second drive wheel 50,which is the inside wheel in a right steering input. Depending onmanufacturing tolerances and component set up, second steering cam 691may need to be offset slightly from 0 degrees with respect to the firststeering cam 681.

Referring now to FIGS. 15 and 16, a reverse input 80 comprises in thisembodiment a reverse pedal 81. The reverse pedal 81 is rotatably mountedto the frame 11 via a reverse pedal pivot 82 in a location easilyaccessible to the user. The reverse pedal pivot 82 is connected to afirst reverse link 83 at a first end 83 a thereof. A second end 83 b ofthe first reverse link 83 is connected to a reverse linkage shaft 84.The reverse linkage shaft 84 is pivotally connected to the frame 11. Asecond reverse link 85 has a first end 85 a and a second end 85 b. Thefirst end 85 a of the second reverse link 85 is connected to the reverselinkage shaft 84. The second end 85 b of the second reverse link 85 isconnected to each pump arm 46, 56 on the pump forward control assembly480 at a location thereon that is on a side opposite its axis ofrotation 480 c. In this manner, when the reverse pedal 81 is depressed,first reverse link 83 pivots the reverse linkage shaft 84 in a mannerthat moves second reverse link 85 in a forward direction, but theforward motion of second reverse link 85 rotates the pump arms 46, 56and swash plates 47, 57 in a rearward direction, equally. Obviously themagnitude of the reverse speed can be adjusted by altering the pivotlocation of the second reverse link 85 with respect to the pump forwardcontrol assembly 480. Pump control springs 483, 484 are provided toreturn the pump arms 46, 56 to neutral. Magnetic sensing proximityswitches 485, 486 are also provided to sense neutral position forsafety.

Referring additionally to FIGS. 25 and 26, the backward motion of thepump arms 46, 56 likewise causes the swash plates 47, 57 to movebackward in relation to the amount of reverse input the operator appliesvia the reverse pedal 81. This causes power to be applied to the drivewheels 40, 50 in the reverse direction in an amount proportional to thereverse input applied by the operator. In this embodiment, because thereverse input 80 is not connected to the engagement cam shaft 742,depression of the reverse pedal 81 does not allow differing speeds ofthe drive wheels 40, 50 in reverse. Therefore, when the vehicle 10 isoperated in reverse, steering is accomplished through the turning of thefirst and second steerable front wheels 20, 30 only. Further, in thisembodiment, the reverse direction is favored over the forward directionsuch that if both the forward pedal 71 and the reverse pedal 81 aredepressed simultaneously, the swash plates 47, 57 will tilt backward,and power will be applied to the drive wheels 40, 50 in the reversedirection. This is possible since the second reverse link 85 isconnected directly to the pump arms 46, 56, while the second forwardlink 715 is connected to the pump forward control assembly 480 viaindependent rotational linkage 487. This feature is a safety mechanismfor emergency situations in which an operator may need to immediatelystop or reverse the apparatus 10. It is feared that in such a situation,a panicked operator might depress both the forward and reverse pedals71, 81 simultaneously. Therefore, in such a situation, the reverse pedal81 and its associated linkage is designed to override the forward pedal71, allowing the operator to reverse away from the dangerous situation.

Having described the vehicle according to one preferred embodiment, asummary of its operation in various modes is now provided. Reference isnow also made to FIGS. 25–31 which show the positions of the pump arms46, 56 and associated structures in various modes of operation of thevehicle 10. FIGS. 25 and 27 show the vehicle 10 at rest, that is inneutral with no steering input applied. FIG. 26 shows the vehicle 10 inreverse. As described, the vehicle 10 provides zero turn radius steeringcapability via a multistage steering system.

At slow speeds with little or no steering input, the forward controlshaft 712 has been rotated only slightly and does not move theengagement cam shaft 742 forward sufficiently to place the first andsecond bearings 780, 790 (via the first and second cam followers 750,755) close enough to the first and second steering cams 681, 691 so asto make contact therebetween. At such low steering input, even thoughthe outer surfaces 682, 692 rotate close to the first and secondbearings 780, 790, they do not make contact (see FIG. 19). As a result,turning the steering wheel 72 (either counterclockwise for a left turnor clockwise for a right turn) slightly (for small steering input) doesnot move the first or second bearings backward (recall that the firstends 760 a, 770 a of the first and second push cables 760, 770 areconnected to the cam followers 750, 755). This means that the drivewheels 40, 50, via pump forward control assembly 480, continue to rotateat equivalent forward speeds. This also means that any turning of thevehicle 10 is performed via the front wheel steering system 600, withits associated structures including, e.g., the first and second steeringshafts 63, 65, the various sprockets 64, 66, 640, 650, and theoblongated sprockets 21, 31.

At slow speeds with high steering input, however, the engagement camsystem 740 is activated in such a manner as to provide a zero-radiusturn. At slow speeds, as just described, the first and second camfollowers 750, 755 are moved forward only slightly. However, the outersurfaces 682, 692 comprise portions thereon that contain sufficientlylarge increases in radius from the axis of rotation 680 c. This meansthat when the steering input is high, such as when it is at a maximumamount indicating a zero-radius turn (see FIG. 21), the outer surfaces682, 692 are able to make contact with the first or second bearings 780,790, respectively, to move the pump arm 46, 56 of the inside wheel in abackward direction. Thus, even at low speeds, the vehicle 10 is capableof performing zero-radius turns.

In reverse the vehicle 10 similarly is steered only via the front wheelsteering system 600, but the vehicle 10 uses different systems for this.Referring to FIG. 26, the reverse pedal 81 is connected to a reverselinkage shaft 84 via reverse pedal pivot 82 and first reverse link 83.Depressing the reverse pedal 81 moves first reverse link 83 forward,which rotates pump arms 46, 56 and swash plates 47, 57 backward, inequal amounts. Because the reverse linkage shaft 84 has no connection tothe engagement cam shaft 742, depressing the reverse pedal 81 does notbring the first and second cam followers into proximity with the firstand second steering cams, and, for similar reasons as just stated, noseparate, independent backward movement of pump arms 46, 56 is allowed.

At moderate to high forward speeds, however, the steering wheel 72 iscapable of both steering the steerable front wheels 20, 30 via the frontwheel steering system 600 and providing separate, independent backwardmotion of the pump arms 46, 56. The system providing this capability isthe engagement cam system 740. When the user depresses the forward pedal71, the forward pedal pivot 710 rotates forward, moving first forwardlink 711 forward. This causes two shafts to rotate forward: the forwardcontrol shaft 712 and the engagement cam shaft 742, each with differentresults, described below.

FIGS. 23 and 24 show the relative positions of the components during aleft steering input FIGS. 21 and 22 shown the positions of thecomponents during a right steering input. Now with reference to FIGS.12, 13, 14A, 14B, and 14C, it is seen that first the forward controlshaft 712 rotates forward via its connection to first forward link 711.This in turn moves the second forward link 715 forward since it is alsoconnected to the forward control shaft 712. Because the second forwardlink 715 is connected to the pump forward control assembly 480, theforward movement of the second forward link 715 causes rotation of thepump forward control assembly 480 about its axis of rotation 480 c.Because the first and second pump arms 46, 56 are connected to rotate inequal amounts by rotation of the pump forward control assembly, eachpump arm 46, 56 is rotated forward in equal amounts, causing each drivewheel 40, 50 to rotate at the same speed in a forward direction, causingstraight forward travel.

Second, the engagement cam shaft 742 rotates forward via arm 720. Thisoccurs because the engagement cam roller 730 contacts the first surface741 a of the engagement cam 741 (see FIG. 14A). As the engagement camshaft 742 is rotated (see FIG. 14B), it moves the gusset plate 765forward via gusset plate link 766. Because the housings 760 c, 770 c ofthe first and second push cables 760, 770 are stiffly connected to thegusset plate 765 and are also connected to the first and second camfollowers 750, 755 at their first ends 760 a, 770 a, this forwardmovement moves the first and second cam followers 750, 755 forward. Theengagement cam shaft 742 continues to rotate forward upon furtherpressing of pedal 71 until the cam 741 has rotated into such positionthat the engagement cam roller 730 moves from contacting the firstsurface 741 a to contacting the second surface 741 b (see FIG. 14C). Inthis manner, continued pressing of the pedal 71 can continue to rotatedthe forward control shaft 712 (thus continuing to increase ground speedof the vehicle 10) without further altering the position of the firstand second cam followers 750, 755 with respect to the first and secondsteering cams 681, 691. In effect the design of the engagement cam 741can be seen to provide a maximum limit of forward travel for the firstand second cam followers 750, 755. Between the neutral position and theposition of maximum travel for the first and second cam followers 750,755, the followers 750, 755 allow a variable amount of steering camcontact between the first and second bearings 780, 790 and the first andsecond steering cams 681, 691, respectively.

From the discussion above regarding slow speeds, it is seen that at arange of low speeds with little or no steering input, the rotation ofthe engagement cam shaft 742 does not move the first and second camfollowers 750, 755 close enough for the first and second bearings 780,790 to be contacted by the first and second steering cams 681, 691.However, at more moderate speeds, or at higher steer input, or at acombination of higher speeds and more steer input, once the first andsecond cam followers 750, 755 have moved in a sufficient amount,steering input can then selectively alter the speed of one drive wheelwith respect to the other drive wheel.

Specifically, referring again to FIGS. 23, 24, and 29, if a left turn ismade by the user (by turning the steering wheel 72 counterclockwise),the steering cam shaft 680 rotates the first steering cam 681counterclockwise so that an increasingly larger outer surface 682contacts the first bearing 780. Because the steering cam shaft 680 doesnot translate (it only rotates), the increasingly larger outer surface682 that is rotated onto the first bearing 780 has the effect of pushingthe first bearing 780 (and therefore also first cam follower 750)backward. The more steering input applied, the farther backward thefirst bearing 780 is pushed. This pushing causes the first push cable760 to rotatingly push the pump arm 46 backward in an amountproportional to the amount of the steering input (See FIG. 29). As thepump arm 46 is rotated backward, the speed it applies to the first drivewheel 40 is decreased. As additional steering input up to a maximumsteering input is applied, the pump arm 46 continues to rotate backward(indicating continually reducing speed for first drive wheel 40), andthen moves beyond neutral into reverse (see FIG. 30). At maximumsteering input, the vehicle 10 is able to achieve a zero-radius turn inthe counterclockwise direction.

Similarly, referring to FIGS. 21, 22, and 31, if a right turn is made bythe user (by turning the steering wheel 72 clockwise), the steering camshaft 680 rotates the second steering cam 691 clockwise so that anincreasingly larger outer surface 692 contacts the second bearing 790.Because the steering cam shaft 680 does not translate (it only rotates),the increasingly larger outer surface 692 that is rotated onto thesecond bearing 790 has the effect of pushing the second bearing 790 (andtherefore also second cam follower 755) backward (see FIG. 22). The moresteering input applied, the farther backward the second bearing 790 ispushed. This pushing causes the second push cable 770 to rotatingly pushthe pump arm 56 backward in an amount proportional to the amount of thesteering input. As the pump arm 56 is rotated backward, the speed itapplies to the second drive wheel 50 is decreased (see FIG. 31). Asadditional steering input up to a maximum steering input is applied, thepump arm 56 continues to rotate backward (indicating continuallyreducing speed for second drive wheel 50), and then moves beyond neutralinto reverse. At maximum steering input, the vehicle 10 is able toachieve a zero-radius turn in the clockwise direction.

Optionally, the vehicle 10 can comprise an adjustable removable seatlatch system 100 to provide an automatic, positive catch or lock of aseat mount 13 a to the frame 11. Referring now to FIGS. 32–34, thepreferred adjustable removable seat latch system 100 is described. Theadjustable removable seat latch system 100 comprises a first latch 110and a second latch 120 connected by a shaft 130. In this embodiment thefirst shaft 110 is identical in all major respects to the second latch120. The shaft 130 comprises a tab 131 extending therefrom. A spring 132is connected to the tab 131 and to the frame 11 or the seat mount 13 ain order to provide a spring bias in a first closed or locked position.The first latch 110 further comprises a finger activation portion 111 onone end thereof and a catch portion 112 on a second end thereof. Thecatch portion 112 preferably further comprises an angled section 113terminating in a groove 114. The first latch 110 further comprises astop portion 115 disposed between the finger activation portion 111 andthe catch portion 112. The first latch 110 preferably further comprisesan adjustment block 116 having adjustment holes 117 in both a horizontalplane and a vertical plane. The stop portion 115 preferably abuts theadjustment block 116 when the adjustable removable seat latch system 100is in the first, closed (latched) position. The spring 132 serves tobias the first latch 110 in the closed position. Preferably the shaft130 is rotatably disposed within the adjustment block 116.

When the seat 13 is down and in the closed, or locked position (see FIG.33), the groove 114 surrounds a mating portion of the frame 11. Thegroove 114 comprises a locking surface 114 a that receives a portion ofthe frame 11. The spring 132 maintains the locking surface 114 a of thegroove 114 in interlocking relationship with the frame 11 or the seatmount 13 a. To open, a user simply presses the finger activation portion111 which works against the spring 132 to rotate the first latch 110 andthe second latch 120 via shaft 130 from a first locked position to asecond, unlocked position, wherein a bottom portion of the groove 114 isno longer in interlocking relationship with frame 11 (see FIG. 34). Theuser can then simply lift the seat 13 to perform maintenance thereunder.Then, when the seat is lowered back into its normal position, the angledsection 113 of the first catch 110 and the second catch 120automatically rides along frame 11, increasingly acting against spring132 until groove 114 is reached. At this time, spring 132 snaps thecatch portion 112 toward frame 11, moving the locking surface 114 a ofthe groove 114 into interlocking relationship with the frame 11. In thisway the seat 13 locks automatically, without the user having to engagemanually a locking device.

The removable adjustment block 116, with its adjustment holes 117, allowthe use to adjust the position of the adjustment block 116 to providethe desired amount of force needed to lock or unlock the adjustableremovable seat latch system 100. With its bolted design, the entireadjustable removable seat latch system 100 may be simply and efficientlyremoved from the seat mount 13 a for repair or replacement without theneed to remove the entire seat 13 or seat mount 13 a.

An embodiment has been shown and described, but variations of theadjustable removable seat latch system 100 are possible withoutdeviating from the invention. For instance, a single seat latch 110 ispossible on either side of the seat mount 13 a without connection (viashaft 130) to a second seat latch 120. Also, the adjustment block 116may include multiple holes instead of slotted adjustment holes 117 toprovide adjustability. Moreover, the slotted holes or multiple holes maybe placed instead in the seat mount 13 a to be used with round holes inthe adjustment block 116. Furthermore, the adjustment block 116 need notbe the device that receives catch portion 112. Rather, catch portion 112could just as easily be received by a portion of the seat mount 13 a orthe frame 11, depending on design of the vehicle 10. Moreover, thegroove 114 could interlock with the frame 11, the seat mount 13 a, orany sturdy feature of the vehicle 10, depending on the specific designsemployed. Regardless of these variations, the adjustable removable seatlatch system 100 provides a safe, reliable, automatic, removable,adjustable seat latch system that provides a positive latch required inROPS systems, without the need for the user to remember to activate asafety latch.

Optionally, the vehicle 10 comprises a cruise control system 950 toallow the operator to remove his/her foot from the forward pedal 71while still maintaining a constant forward speed. Referring to FIGS. 35and 36, the cruise control system 950 of this embodiment comprises ahandle 951 rotatably connected to the frame 11 at a pivot 952. The pivot952 preferably comprises a spring 953 to bias the handle 951 in anengaged position.

The handle 951 comprises an arm 954 connected to a cruise control shaft955 that is rotatably connected to the frame 11. The cruise controlshaft 955 has a first end 955 a and a second end 955 b. The first end955 a is connected to the arm 954. A first cruise control link 956,having a first end 956 a and a second end 956 b, is connected at itsfirst end 956 a to the second end 955 b of the cruise control shaft 955via arm 955 c. The second end 956 b of the first cruise control link 956is connected to a forward control arm 957 that is rotatably connected tothe forward control shaft 712. The forward control arm 957 furthercomprises an engagement tab 958 extending outwardly therefrom. Theengagement tab 958 engages the arm 713 at the first forward link 711.

The handle 951 is moveable within a slot 951 a Notches 951 b are locatedwithin the slot 951 a When a user pushes handle 951 forward, thisrotates cruise control shaft 955 forward, thereby moving first cruisecontrol link 956 forward. Forward control arm 957 then moves engagementtab 958 into engagement with arm 713 of forward control shaft 712.Further movement of handle 951 then rotates forward control shaft 712forward. Because first forward link 711 is now being moved forward, thistranslates into forward movement of the vehicle 10. Additional movementof handle 951 translates into increased ground speed of the vehicle 10.Spring loaded pivot 952 biases handle 951 into notches 951 b within slot951 a The user is then able to select the desired ground speed of thevehicle 10 and allow the handle 951 to reside in an appropriate notch951 b. In this manner the user is operating in cruise control and canremove his foot from forward pedal 71.

As stated above, and with reference again to FIGS. 1 and 4, the presentinvention optionally may be adapted for use as a lawn mower. To thatend, a mowing deck 14 may be attached to frame 11 comprising one or morecutting blades 15 for use in cutting grass. The mowing deck 14 may beany type of cutting deck known in the art for use with a lawn mower,however the present invention is particularly suited for use with amowing deck 14 comprising counter-rotating blades 15. Further, eachcutting blade 15 may rotate within its own individual blade chamber 16during operation. The cutting blades 15 counter-rotate in that one ormore of the blades rotates in the clockwise direction during operationwhile one or more of the other blades rotates in the counterclockwisedirection. The paths of these counter-rotating blades 15 may overlap,with the blade chambers 16 having an opening in such area to allow forthe overlapping. The mowing deck 14 may include an exit chute 17 toallow the grass clippings to exit the mowing deck 14 after cutting. Theexit chute 17 may be placed at a variety of locations on the apparatus10, such as on the left or right side of the mowing deck 14 or at therear of the apparatus 10, among others. Further, the blade chambers 16may include enclosures in which grass clippings are kept after cuttingin order to prevent them from exiting the mowing deck 14 area andlittering the lawn.

Optionally the vehicle 10 may comprise an automatic height adjustmentmeans 140 for the mowing deck 14. Referring now to FIG. 37, in thisembodiment the automatic height adjustment means 140 comprises a motor141 electrically connected to a switch 142 mounted in a convenientlocation on the control panel 18 for the user. The motor 141 comprises amovable actuator 143. The actuator 143 is connected to various heightadjustment linkages 144 that translate the linear motion of the actuator143 into vertical height adjustment of the mowing deck 14, keeping themowing deck 14 level during its travel. In the preferred embodiment, themotor 141 is a linear actuator such as manufactured by Dollinger.

While there has been described and illustrated particular embodiments ofa novel ZTR vehicle with steerable front wheels and a multistagesteering system, it will be apparent to those skilled in the art thatvariations and modifications may be possible without deviating from thebroad spirit and principle of the present invention, which shall belimited solely by the scope of the claims appended hereto.

1. A zero-turn radius vehicle comprising: a frame; an engine operativelyconnected to said frame; first and second steerable front wheelsrotatably mounted to said frame; first and second drive wheels rotatablymounted to said frame; a front wheel steering system further comprisinga steering cam shaft having a first steering cam and a second steeringcam rotatably mounted to said steering shaft at a first axis ofrotation, and at least one steering sprocket rotatably mounted to saidsteering cam shaft at said first axis of rotation for meshingly engaginga first wheel sprocket associated with said first steerable front wheeland a second wheel sprocket associated with said second steerable frontwheel; a first pump having a pump shaft operatively connected to saidfirst drive wheel and having a pump arm operatively connected to a swashplate rotatable in a forward direction and a reverse direction forcontrolling an amount and a direction of power output from said firstpump to said first drive wheel; a second pump having a pump shaftoperatively connected to said second drive wheel and having a pump armoperatively connected to a swash plate rotatable in a forward directionand a reverse direction for controlling an amount and a direction ofpower output from said second pump to said second drive wheel; a forwardcontrol assembly having a forward control shaft rotatably connected tosaid frame and receiving an input from a forward input device, saidforward control assembly being operatively connected to said pump armsof said first and second pumps via a pump forward control assembly andproviding an equal forward rotation of said pump arms; an engagement camsystem having an engagement cam shaft rotatably mounted to said frameand an engagement cam disposed on said engagement cam shaft, whereinsaid engagement cam shaft is operatively connected to a first and secondcam follower, each of which further comprises first and second bearings,respectively; a first push cable having a first end and a second endconnected at its first end to said first cam follower and connected atits second end to said pump arm of said first pump; and a second pushcable having a first end and a second end connected at its first end tosaid second cam follower and connected at its second end to said pumparm of said second pump.
 2. The zero-turn radius vehicle according toclaim 1 wherein said first steering cam further comprises a portion of aperimeter having an increasing radius in a clockwise direction aboutsaid first axis of rotation.
 3. The zero-turn radius vehicle accordingto claim 2 wherein said increasing radius increases in a relationshipselected from the group consisting of parabolic, hyperbolic, elliptical,curvate, and spiral.
 4. The zero-turn radius vehicle according to claim3 wherein said forward input comprises a pedal.
 5. The zero-turn radiusvehicle according to claim 4 wherein said pedal is operatively connectedto a first forward link that is connected to said forward control shaft.6. The zero-turn radius vehicle according to claim 5 wherein saidforward control shaft is operatively connected to a second forward linkthat is connected to said pump forward control assembly.
 7. Thezero-turn radius vehicle according to claim 6 wherein said pump forwardcontrol assembly is rotatable in forward and reverse directions about anaxis of rotation coincident with said first axis of rotation.
 8. Thezero-turn radius vehicle according to claim 7 wherein said pump forwardcontrol assembly further comprises a contact plate for receiving saidpump arm of said first pump and said pump arm of said second pump. 9.The zero-turn radius vehicle according to claim 8 wherein saidengagement cam further comprises a first surface and a second surface,wherein said second surface is disposed at an angle from said firstsurface.
 10. The zero-turn radius vehicle according to claim 9 whereinsaid forward input further comprises an arm having a cam roller disposedthereon.
 11. The zero-turn radius vehicle according to claim 10 whereinupon rotation of said forward control shaft, said cam roller engagessaid first surface of said engagement cam.
 12. The zero-turn radiusvehicle according to claim 11 wherein upon engagement of said cam rollerwith said first surface of said engagement cam, said engagement camshaft is thereby rotated in a forward direction.
 13. The zero-turnradius vehicle according to claim 12 wherein upon rotation of saidengagement cam shaft, said first cam roller and said second cam rollermove forward in closer proximity to said first and second steering cams,respectively.
 14. The zero-turn radius vehicle according to claim 13wherein said first cam follower and said second cam follower reachmaximum forward positions at approximately the point where said camroller moves from contacting said first surface of said engagement camto contacting said second surface of said engagement cam.
 15. Thezero-turn radius vehicle according to claim 14 wherein furtheractivation of said forward pedal results in increased speed of saidvehicle.
 16. The zero-turn radius vehicle according to claim 1 whereinsaid second steering cam further comprises a portion of a perimeterhaving an increasing radius in a counterclockwise direction about saidfirst axis of rotation.
 17. The zero-turn radius vehicle according toclaim 16 wherein said increasing radius increases in a relationshipselected from the group consisting of parabolic, hyperbolic, elliptical,curvate, and spiral.
 18. The zero-turn radius vehicle according to claim17 wherein said forward input comprises a pedal.
 19. The zero-turnradius vehicle according to claim 18 wherein said pedal is operativelyconnected to a first forward link that is connected to said forwardcontrol shaft.
 20. The zero-turn radius vehicle according to claim 19wherein said forward control shaft is operatively connected to a secondforward link that is connected to said pump forward control assembly.21. The zero-turn radius vehicle according to claim 20 wherein said pumpforward control assembly is rotatable in forward and reverse directionsabout an axis of rotation coincident with said first axis of rotation.22. The zero-turn radius vehicle according to claim 21 wherein said pumpforward control assembly further comprises a contact plate for receivingsaid pump arm of said first pump and said pump arm of said second pump.23. The zero-turn radius vehicle according to claim 22 wherein saidengagement cam further comprises a first surface and a second surface,wherein said second surface is disposed at an angle from said firstsurface.
 24. The zero-turn radius vehicle according to claim 23 whereinsaid forward input further comprises an arm having a cam roller disposedthereon.
 25. The zero-turn radius vehicle according to claim 24 whereinupon rotation of said forward control shaft, said cam roller engagessaid first surface of said engagement cam.
 26. The zero-turn radiusvehicle according to claim 25 wherein upon engagement of said cam rollerwith said first surface of said engagement cam, said engagement camshaft is thereby rotated in a forward direction.
 27. The zero-turnradius vehicle according to claim 26 wherein upon rotation of saidengagement cam shaft, said first cam roller and said second cam rollermove forward in closer proximity to said first and second steering cams,respectively.
 28. The zero-turn radius vehicle according to claim 27wherein said first cam follower and said second cam follower reachmaximum forward positions at approximately the point where said camroller moves from contacting said first surface of said engagement camto contacting said second surface of said engagement cam.
 29. Thezero-turn radius vehicle according to claim 28 wherein furtheractivation of said forward pedal results in increased speed of saidvehicle.
 30. The zero-turn radius vehicle according to claim 1 whereinsaid first wheel sprocket is oblongated.
 31. The zero-turn radiusvehicle according to claim 30 wherein said first steering cam furthercomprises a portion of a perimeter having an increasing radius in aclockwise direction about said first axis of rotation.
 32. The zero-turnradius vehicle according to claim 31 wherein said increasing radiusincreases in a relationship selected from the group consisting ofparabolic, hyperbolic, elliptical, curvate, and spiral.
 33. Thezero-turn radius vehicle according to claim 32 wherein said forwardinput comprises a pedal.
 34. The zero-turn radius vehicle according toclaim 33 wherein said pedal is operatively connected to a first forwardlink that is connected to said forward control shaft.
 35. The zero-turnradius vehicle according to claim 34 wherein said forward control shaftis operatively connected to a second forward link that is connected tosaid pump forward control assembly.
 36. The zero-turn radius vehicleaccording to claim 35 wherein said pump forward control assembly isrotatable in forward and reverse directions about an axis of rotationcoincident with said first axis of rotation.
 37. The zero-turn radiusvehicle according to claim 36 wherein said pump forward control assemblyfurther comprises a contact plate for receiving said pump arm of saidfirst pump and said pump arm of said second pump.
 38. The zero-turnradius vehicle according to claim 37 wherein said engagement cam furthercomprises a first surface and a second surface, wherein said secondsurface is disposed at an angle from said first surface.
 39. Thezero-turn radius vehicle according to claim 38 wherein said forwardinput further comprises an arm having a cam roller disposed thereon. 40.The zero-turn radius vehicle according to claim 39 wherein upon rotationof said forward control shaft, said cam roller engages said firstsurface of said engagement cam.
 41. The zero-turn radius vehicleaccording to claim 40 wherein upon engagement of said cam roller withsaid first surface of said engagement cam, said engagement cam shaft isthereby rotated in a forward direction.
 42. The zero-turn radius vehicleaccording to claim 41 wherein upon rotation of said engagement camshaft, said first cam roller and said second cam roller move forward incloser proximity to said first and second steering cams, respectively.43. The zero-turn radius vehicle according to claim 42 wherein saidfirst cam follower and said second cam follower reach maximum forwardpositions at approximately the point where said cam roller moves fromcontacting said first surface of said engagement cam to contacting saidsecond surface of said engagement cam.
 44. The zero-turn radius vehicleaccording to claim 43 wherein further activation of said forward pedalresults in increased speed of said vehicle.
 45. The zero-turn radiusvehicle according to claim 1 wherein said second wheel sprocket isoblongated.
 46. The zero-turn radius vehicle according to claim 45wherein said second steering cam further comprises a portion of aperimeter having an increasing radius in a counterclockwise directionabout said first axis of rotation.
 47. The zero-turn radius vehicleaccording to claim 46 wherein said increasing radius increases in arelationship selected from the group consisting of parabolic,hyperbolic, elliptical, curvate, and spiral.
 48. The zero-turn radiusvehicle according to claim 47 wherein said forward input comprises apedal.
 49. The zero-turn radius vehicle according to claim 48 whereinsaid pedal is operatively connected to a first forward link that isconnected to said forward control shaft.
 50. The zero-turn radiusvehicle according to claim 49 wherein said forward control shaft isoperatively connected to a second forward link that is connected to saidpump forward control assembly.
 51. The zero-turn radius vehicleaccording to claim 50 wherein said pump forward control assembly isrotatable in forward and reverse directions about an axis of rotationcoincident with said first axis of rotation.
 52. The zero-turn radiusvehicle according to claim 51 wherein said pump forward control assemblyfurther comprises a contact plate for receiving said pump arm of saidfirst pump and said pump arm of said second pump.
 53. The zero-turnradius vehicle according to claim 52 wherein said engagement cam furthercomprises a first surface and a second surface, wherein said secondsurface is disposed at an angle from said first surface.
 54. Thezero-turn radius vehicle according to claim 53 wherein said forwardinput further comprises an arm having a cam roller disposed thereon. 55.The zero-turn radius vehicle according to claim 54 wherein upon rotationof said forward control shaft, said cam roller engages said firstsurface of said engagement cam.
 56. The zero-turn radius vehicleaccording to claim 55 wherein upon engagement of said cam roller withsaid first surface of said engagement cam, said engagement cam shaft isthereby rotated in a forward direction.
 57. The zero-turn radius vehicleaccording to claim 56 wherein upon rotation of said engagement camshaft, said first cam roller and said second cam roller move forward incloser proximity to said first and second steering cams, respectively.58. The zero-turn radius vehicle according to claim 57 wherein saidfirst cam follower and said second cam follower reach maximum forwardpositions at approximately the point where said cam roller moves fromcontacting said first surface of said engagement cam to contacting saidsecond surface of said engagement cam.
 59. The zero-turn radius vehicleaccording to claim 58 wherein further activation of said forward pedalresults in increased speed of said vehicle.
 60. A zero-turn radiusvehicle comprising: a frame; an engine operatively connected to saidframe for providing power to said vehicle; at least one steerable frontwheel rotatably mounted to said frame; first and second independentlypowered drive wheels rotatably mounted to said frame; a pump mechanismoperatively connected to said first and second independently powereddrive wheels having a pump arm rotatably movable in a first directionand a second direction about a first axis of rotation for providingpower to said first and second independently powered drive wheels in afirst direction and a second direction; a means for steering said atleast one steerable front wheel via a steering input; a forward controlassembly further comprising a means for providing equal rotation of saidfirst and second independently powered drive wheels in a forwarddirection via a forward input; a means for coupling said forward inputto said forward control assembly; and a means for linking said steeringinput to said pump mechanism so as to drive said first and secondindependently powered drive wheels at unequal velocity; wherein saidmeans for steering said at least one steerable front wheel furthercomprises a steering cam shaft rotatably disposed about a second axis ofrotation; wherein said steering cam shaft further comprises a steeringcam having a portion of an outer perimeter having an increasing radiusin a first direction about said second axis of rotation; wherein saidmeans for rotatably coupling said forward input to said forward controlassembly comprises at least one forward link coupled to a rotatablymounted forward control shaft; and wherein said forward control shaftfurther comprises an arm disposed outwardly therefrom.
 61. The zero turnradius vehicle of claim 60 wherein said forward link comprises a tab forcontacting said arm of said forward control shaft.
 62. The zero turnradius vehicle of claim 61 wherein once said tab contacts said arm,further forward input results in additional rotation of said forwardcontrol shaft.
 63. The zero turn radius vehicle of claim 62 wherein saidmeans for linking said steering input to said pump mechanism furthercomprises a cam follower movably mounted to said frame.
 64. The zeroturn radius vehicle of claim 63 wherein said cam follower furthercomprises a bearing mounted thereto.
 65. The zero turn radius vehicle ofclaim 64 wherein said cam follower further comprises a push cableconnected thereto.
 66. The zero turn radius vehicle of claim 65 whereinsaid cam follower is connected to a gusset plate that is rotatablymounted to said frame.
 67. The zero turn radius vehicle of claim 66wherein as said forward input is provided, said cam follower and saidgusset plate move in a forward direction in proportion to an amount ofsaid forward input.
 68. The zero turn radius vehicle of claim 67 whereina first steering input moves said cam into surface contact relationshipwith said bearing.
 69. The zero turn radius vehicle of claim 68 whereinsaid bearing moves backward as a result of said first steering input.70. The zero turn radius vehicle of claim 69 wherein said push cablerotates said pump arm backward about said first axis of rotation inproportion to an amount of said first steering input.
 71. The zero turnradius vehicle of claim 70 wherein said vehicle further comprises areverse control assembly comprising a means for coupling said pump armfor equal rotation in a reverse direction.
 72. A zero turn radiusvehicle comprising: a frame; an engine operatively connected to saidframe; at least one steerable front wheel rotatably connected to saidframe and operatively connected to a steering device; first and seconddrive wheels rotatably mounted to said frame; a front wheel steeringsystem further comprising a steering cam shaft having at least onesteering cam rotatably mounted thereon about a first axis of rotation,wherein said at least one steering cam further comprises an externalsurface having an increasing radius in a given circumferential directionabout said first axis of rotation; and a means for directing locomotivepower independently to said first and second drive wheels in response toa steering input from said steering device.
 73. A zero-turn radiusvehicle comprising: a frame; an engine operatively connected to saidframe; first and second independently powered drive wheels rotatablymounted to said frame; at least one steerable front wheel rotatablymounted to said frame; a front wheel steering system having at least onesteering cam rotatably mounted to a steering cam shaft at a first axisof rotation, and at least one steering sprocket rotatably mounted tosaid steering cam shaft at said first axis of rotation for meshinglyengaging a wheel sprocket associated with said at least one steerablefront wheel; a first pump having a pump shaft operatively connected tosaid first independently powered drive wheel and having a pump armoperatively connected to a swash plate rotatable in a forward directionand a reverse direction for controlling an amount and a direction ofpower output from said first pump to said first drive wheel; a secondpump having a pump shaft operatively connected to said secondindependently powered drive wheel and having a pump arm operativelyconnected to a swash plate rotatable in a forward direction and areverse direction for controlling an amount and a direction of poweroutput from said second pump to said second drive wheel; a forwardcontrol assembly operatively connected to said pump arms of said firstand second pumps providing an equal forward rotation of said pump arms;a forward control shaft rotatably connected to said frame and receivingan input from a forward input device an engagement cam shaft rotatablymounted to said frame having an engagement cam disposed thereon, whereinsaid engagement cam shaft is operatively connected to at least one camfollower; a first cable having a first end and a second end and beingconnected at its first end to said at least one cam follower andconnected at its second end to said pump arm of said first pump; and asecond cable having a first end and a second end and being connected atits first end to said at least one cam follower and connected at itssecond end to said pump arm of said second pump.